I have a Client who has a 2Kw array on a GVFX 3648 Grid tied inverter w/48Vdc battery (Concorde AGM). It used to work well, now it seems to be spending lots of time eithr sleeping or waking up.what could be the causes of this behavior? If the grid got out of spec, then it should switch to invert, correct? or if the grid getsout of speck it may just stop selling and keep the grid passing thru to inverter subpanel?

"Sleeping occurs when PV voltage is 2 volts less than battery voltage, and wakeup occurs when PV open circuit voltage rises above battery system voltage by 2 volts. This is the behavior you get at dawn and dusk when there's not quite enough power from the PV array to keep going." - paraphrased from MX60 manual.

I was at the site today. Even talked to OutBack rep who suggested we clean PV panels. They are clean. 2 things are happening. The Inverter seems to be not spending enough time selling, even though the bat voltage is up 53-55V (Sell set at 52). PV input is 75, thou I have seen it as low as 60, while putting out amps, and the inverter selling. today is VERY sunny, no clouds so the PV input was very steady. Yet the GTMode, sleeping, waking up, tracking cycles a lot, all the while it is sunny 75volts pv in. 12 Sharp 72cell 170 watt, only 2 in series, 6 pv input breakers. All test Voc around 83V. Imp at combiner while output was hot were all nominally the same (about 3amps ea x 6 18a pv in)the the mate shows the inverter cycling into charge, briefly, then back to support; Sell RE, but the inverter watts is not there, thou the bats are above 52. I tried to get it to sell down to 49, but it wouldnt go down below 51.9. this doesnt seem normal to me Plseas help

It does sound like maybe the grid is going out of spec, but if it is you should see a red light (flashing red for a warning, solid red for a shutdown error) on the inverter. There's a DISCONNECT menu on the Mate where you can see the reason for the last disconnect from the grid.

I know where I live, most houses are heated electrically, and in the springtime my inverters often disconnect from selling as heating loads drop off, system voltage increases before my utility changes the taps on the feed transformers to send out a lower voltage. Don't know where you're at but maybe high temps are increasing air conditioning loads and dropping your AC voltage below the FX spec. Just "spec"ulating here...

Yes, the last stop sell was #2 which is "island detected, or, wobble"also seen the grid voltage range from 130 to low 120 within short time at site. At 130 it was selling though. and yes, the red error lite on inverter flashes intermitintly, from time to time, time always posting a warning or error message. thou I have seen error msg of grid over and under voltage as well as one more I cant remember. How do you clear error msgs? the owner did mention that the inverter seems to do a better job selling when he has his 240Vac pool pump on, (run by grid)btw, I am in St Croix, US Virgin Islands. got a solar bus here since 1980. tried to edit profile to post that by my name, but couldnt see how.

If the system sells better when he's running his pool pump, the grid voltage (and/or maybe frequency - "wobble") is probably running too high and the pump motor is dragging it down enough to allow him to sell. Unfortunately, I don't think there's much you can do about grid quality except maybe complain to the local authority. Is there a lot of solar development coming on line down there? If so that could be a contributing factor (until the power authority figures out how to deal with it).

I wouldn't worry about clearing the error messages, they won't affect operation AFAIK.

I just remembered, there is one thing you can do to expand the voltage and frequency windows that his inverter operates in. On the SELL menu on the Mate there's a Grid Tie Window option that defaults to IEEE. If you change it to USER, you may reduce the nuisance disconnects your customer is having. However, the directions in my inverter manual say "This function should not, I repeat, should not be changed without consulting Outback Power Systems first". That's verbatim, and their emphasis, not mine.